Data storage is an increasingly crucial and central part of many industries dealing in financial transactions and other sensitive tasks, such as banks, government facilities/contractors, defense, health care institutions, pharmaceutical companies and securities brokerages. In many of these environments, it is necessary to store selected data in an immutable and unalterable manner. Forms of data that require immutable treatment often include e-mails, financial documents and transaction records, and any other record that may act as proof of an important action or decision. Even in less-critical/unregulated environments, the ability to store a secure unalterable data cache is highly desirable. For example engineering, medical, law and other professional firms may wish to establish a cache of key data (e.g. invention reports or design files, client communications, medical images, etc.), that will remain unaltered and online for long periods on time. These caches can provide reliable references and proofs for clients and other interested parties.
There are a number of government regulations that require a variety of data records be available for retrieval, for a specified period of time, from non-modifiable, non-erasable archives. For example, Securities and Exchange Commission (SEC) Rule 17a-4 (i.e., 17 C.F.R. §240.17a-4, hereinafter “the Rule”) requires that certain stock exchange members, brokers, and dealers maintain certain records for a period of time (typically three or seven years). This data must therefore be archived for the period of time specified by the Rule in order to comply with the Rule. There may be various other reasons to store certain data for at least a predetermined period of time. A compliant storage service is used to store data reliably and without altering for a predetermined period that may be set by an administrator, predetermined by a manufacturer of the storage system, etc. “Compliant” storage refers to data storage that complies with predetermined requirement. Compliance generally requires that the data must be archived and cannot be deleted or modified until the end of the period for which it must be retained.
Some existing systems utilize a secure compliance clock to gauge the time relative to the retention period. A compliance clock uses a trusted time base (a source of the current time value that is as a reliable source), such as a repetitive file server process, to derive its time value. A file server is a computer attached to a network that has the primary purpose of providing a location for the shared storage of computer files. The clock may be designed to be tamper-resistant, and its time value (that is measured with respect to a value initially set by an administrator) is increased in a manner that the retention period is never reduced, but may be longer to further ensure observance of the full retention period. Alternatively, the clock can be based upon a trusted third-party clock (such as a government-based clock) or an additional secure hardware-based clock. In existing systems, compliance clock falls behind when a volume is powered down, etc., which may result the actual retention time to be greater than the required retention time and thus cause inefficient use of storage resources. A “volume” is a set of stored data associated with a collection of mass storage devices, such as disks, which obtains its storage from (i.e., is contained within) an aggregate, and which is managed as an independent administrative unit.